The deleterious effects of compositions containing surfactants upon keratin are well known. These effects are caused, it is thought, by penetration of the surfactant into the keratin surface leading to "leaching out" of oils and moisturizing components essential for good condition of the keratin. This penetration by surfactant and "leaching out" of essential oils also affects the ability of the keratin, particularly in the case of skin, to retain water within the tissue and this again leads to poor condition of the keratinous material.
Many attempts have been made in the past to provide compositions for maintaining or improving the condition of skin and hair. The application of protein to skin and hair as cosmetic treatments probably antedates recorded history. Casein, in the form of milk, has been used as a time-honoured beautifier and more recently has been recommended for use in toilet soaps. U.K. Pat. No. 1,160,485 describes the inclusion of partially degraded water soluble proteins having a gel strength of zero Bloom grams in detergent compositions and lotions for application to skin as dishwashing liquids.
German Offenlegungsschriften (Published Specifications) Nos. 2,151,739 and 2,151,740 describe certain fatty derivatives of low-molecular-weight aminolysates suitable for use in shampoos. U.K. Pat. No. 1,122,076 describes the preparation of low-molecular-weight, alcohol-soluble protein esters suitable for use in hair-spray formulations. Various low-molecular-weight polypeptides or modified polypeptides are commercially available and recommended for use in cosmetic and shampoo formulations, for instance Hydro Pro 220, and Hydro Pro 330 marketed by the Stepan Chemical Company; and Wilson X250, Wilson X1000 and Wilson Aqua Pro marketed by the Wilson Chemical Company. However, it has been found that none of these compositions are especially effective in protecting keratin from the action of harsh detergents, and this is particularly true when the proteins are incorporated in the detergent composition itself. The emolliency of these compositions can often be improved by addition of fatty or oily materials but, when used in dishwashing liquids, this usually leads to loss of foaming power or aesthetic changes which are generally considered undesirable by consumers.